Total Border Security Surveillance

Transcription

1 Total Border Security Surveillance Item Type text; Proceedings Authors Herold, Fredrick W. Publisher International Foundation for Telemetering Journal International Telemetering Conference Proceedings Rights Copyright International Foundation for Telemetering Download date 9/06/08 0::5 Link to Item

2 Total Border Security Surveillance Fredrick W. Herold Fredrick Herold & Associates, Inc. ABSTRACT This paper describes a system of Total Border Surveillance, which is cost effective, closes existing gaps and is less manpower intensive than the current techniques. The system utilizes a fleet of commercially available aircraft converted to unmanned capability, existing GPS and surveillance systems and autonomous ground stations to provide the desired coverage. KEY WORDS Unmanned aerial vehicles, autonomous ground terminals, FLIR Systems, GPS, auto pilot, retrodirective phased array and Code Division Multiple Access (CDMA) Fredrick Herold & Associates, Inc (FH&A) has developed and patented a retrodirective feature into a phased array, which, while using no moving parts or software, can instantly develop and form a beam on, as well as display pointing information from a beacon or a received source. FLIR Systems possesses the technology for detection of vehicles, people or surface vessels using various active and passive technologies. Both FLIR and FH&A have vast experience in data transfer technologies and ground station implementation. These two companies, in conjunction with Liberty Aircraft, have formulated the following plan for a low cost, high yield method of providing constant surveillance of all border areas of the United States or any other designated area. Basically, the method utilizes a string of Unmanned Aerial Vehicles (UAVs) and a complementary series of unmanned Autonomous Ground Stations. The example shown is for the East coast of the United States, but can be applied to all borders and to any area where sensor technology is desired. A dedicated fleet of UAVs along with two or more maintenance and refueling crews would be assigned to the example aircraft fleet. A string of Autonomous Ground Stations would be constructed and spaced at approximately one hundred mile intervals. These stations and the unmanned aircraft would use the retrodirective technology mentioned earlier. Each of the UAVs would be equipped with the appropriate sensors for the mission(s) to be accomplished. Note, that multiple missions can be supported simultaneously; i.e., TV cameras installed for search and rescue missions or visual detection of intruders, along with the anti-submarine detection devices, such as magnetometers and advanced infrared detection for surface vehicles.

3 Assuming a one hundred knot cruise speed for the UAVs, they would be launched from Bangor, Maine and programmed to fly at a predetermined distance from the U.S. coast. The UAVs would have a retrodirective array embedded in the structure of the airframe, which would permit two-way communication with the autonomous ground stations. The aircraft would use either a Code Division Multiple Access (CDMA) System or a frequency separation for non-ambiguous identification and would be launched at half hour intervals giving (no wind) a fifty nautical mile (NM) separation. This would insure virtually uninterrupted coverage of the entire coastline. The UAVs would be landed at Key West, Florida and possibly an intermediate location such as Charleston South Carolina, to be refueled and serviced, then sent back to Bangor, Maine at time intervals that would increase the coverage of the coastline. The Autonomous Ground Stations would be designed to house the receivers in sufficient quantities, including self-switching spares, to simultaneously receive the inputs from all UAVs within range. Since the retrodirectivity of the system insures tight beams, interference would be difficult where CDMA are used, since the interferer would require so much power that detection and location of the interference is virtually assured. The data from all of the autonomous stations would be routed either via satellite transmission, dedicated landlines or via high speed Internet to a master control station. The master station would be receiving the GPS location of each UAV, with the precise direction of the detected threat from the UAV, time and, if possible, range. The range can be readily determined by triangulation, as the threat will most probably be detected by multiple UAVs. The use of one (or more) master stations and the fact that all coastal stations can be unmanned will drastically reduce the amount of manpower required to provide twenty four hour a day, seven days a week manning. The entire operation could be accomplished with a total force of two hundred (00) trained personnel for each border. This assumes sixty (60) aircraft and equipment personnel at the Bangor and Key West locations and eighty (80) for the master control station. Out of the eighty (80) located at the master control station twenty will be used for servicing of the autonomous stations. Similar networks can be set up for all borders and a scheme can be set up to guard the perimeter of a carrier task force. The UAVs would be considerably less expensive then the current Predator type of UAV. The Liberty Aircraft was chosen as the desired platform for this task for the following reasons:. The Liberty Aircraft is a fully certificated, all weather aircraft capable of carrying payloads in excess of 400 pounds while fully loaded with fuel. Fuel load can therefore be increased to add range while still maintaining a high payload capacity.. The Liberty Aircraft can be equipped with a tried and true autopilot such as the S. Tech Model 55. This model is recommended, as it can be programmed to climb and descend at fixed rates, can automatically level the aircraft at preset altitudes and can follow a preprogrammed onboard GPS course.

4 . The Liberty Aircraft has a standard continental engine (Model 40), which is fuel injected and has a FADEC System (Full Authority Digital Engine Control), which eliminates the need for mixture adjustments and also eliminates the danger of carburetor icing. 4. The combination of standard aircraft, off the shelf Auto Pilot and an engine that any civilian A&P is qualified to repair or replace, will greatly reduce down time and simplify maintenance and cost. 5. The factories and technical expertise for the aircraft, engine, autopilot, GPS and control systems are located within the continental U.S., insuring rapid response and continuing availability of expertise to keep the system intact. The FLIR System was chosen for the surveillance package for the following reasons:. FLIR has been manufacturing systems for the military and law enforcement agencies for several years.. These systems have been mounted on helicopters, which have a more hostile environment then the proposed aircraft and have proven performance.. The systems are adaptable and versatile and can be custom built to satisfy specific threat detection. It is intended that these aircraft will be transponder equipped to enable the FAA to steer traffic around them and the altitude encoders will alert the master control station of any anomalies. Figure shows the detection scheme envisioned and Figure shows the enhanced coverage. Ground stations for satellite communications that are manned three shifts per day/seven days a week have become increasingly expensive to operate and maintain. In addition, there are situations where a ground station is only needed in a particular area for a short period of time. A portable system, which could be employed in another location at a later time, would be the ideal solution, i.e., a readily transportable system. Employment of the retro-directive technique described in refs. and presents the possibility of a totally Autonomous Ground Station that provides both hemispheric coverage and continuous tracking. This System also eliminates the keyhole found in most dish antenna systems. The System envisioned would establish communications between a UAV and the ground station without requiring human intervention or moving parts, and, using an error signal developed in Reference, offers the possibility of nulling unwanted signals. When a UAV is to be in view, the ground station beacon antenna, using, for example, Code Division Multiple Access (CDMA), turns on the desired UAV transmitter and directs its retro-directive or tracking beam to the ground station. The ground station in turn, using the UAV transmitted signal, phases-up its receive and transmit arrays so as to point the ground station beams to the UAV, thereby establishing twoway communications. The process is automatic and provides continuous horizon to horizon tracking. Use of the CDMA to separate the user UAV would allow simultaneous communications with multiple UAVs, while providing 0 db separation when using the gold codes.

5 This System requires no apriori knowledge of source location. It is totally automated, requires very little maintenance and no manual intervention; and over its lifetime should prove cost effective. Figure shows a typical system configuration, while Figure 4 is a suggested antenna arrangement for X-Band. Each of the four arrays in Figure 4 provides coverage in excess of 50 in both elevation and azimuthal planes, thereby providing total hemispheric coverage. The sequence of operations would call for the ground station to send an omni-directional beacon signal that turns on the desired vehicle. This signal should be of narrow bandwidth to reduce the power requirements. The UAV, in turn, transmits a signal that allows the ground station to phase-up both the transmit and receive arrays, so as to point their beams to the UAV, thereby establishing two-way communications. As described in Reference, the ground station receive array employs a few sensor elements arrayed both horizontally and vertically, that measure phase differences generated by the UAV signal incident on the sensor elements. This is known as a thinned array. A total of nine sensor elements in each planar array of Figure 4 are sufficient to generate all phases required to scan each planar array in both planes, i.e., in azimuth and elevation. The only software required for the system to operate is that which seeds the ground station beacon, so as to turn-on the desired vehicle. Thereafter, signal acquisition, beam formation and tracking is automatic. This requires no phase shifters, moving parts or a priori knowledge of signal source location. Complete hemispheric coverage is thereby achieved by employing four planar arrays, as shown in Figure 4, each mounted on a face of a four sided pyramid inclined at 45. Radiation coverage by each array is greater than 45, thereby providing continuous coverage over the entire hemisphere, both in elevation and in azimuth. Receive and transmit phases for each of the array elements are determined by measuring quantities containing the phase differences generated by a signal incident on a few interferometer pairs, i.e. on thinned arrays. The need for phase shifters or switches is eliminated. By generating a radiation pattern that is orthogonal to the conventional sum pattern, nulling of unwanted signals is greatly simplified. Nulling of unwanted signals can be accomplished by generating two independent radiation patterns using the same receiver array. First is the conventional sum pattern with its on-axis maximum response and associated side lobes. The second pattern is orthogonal to the first and has a null onaxis rather than a maximum. A summation of appropriate harmonics produces a radiation pattern that approximates a signum function, i.e., a response that is uniformly positive for all positive spatial angles, uniformly negative for all negative spatial angles and zero at array zenith. Figure 5. This zero response is independently scannable relative to the sum channel. Placing the null in the direction of an unwanted signal and multiplying the two antenna patterns eliminate the unwanted signal while not affecting the desired signal. Additional receivers can be added to the same array for multiple user support in a CDMA System with full array gain available to each user simultaneously. Power dividers are placed after

6 amplification of the signal and are routed to each user receiver. The CDMA code is reduced to provide the carrier and information to be processed. Each user would use a separate subset of phase combiners (mixers), which would form independent beams for each user. The Local Oscillators could be shared for all users as the desired directional information is contained in the carrier after removal of the CDMA code. This enables the same array to support multiple users simultaneously. Each user would require the use of a separate array for transmit from the ground station for directivity of the beam. This does not normally pose a problem as the transmit beam usually is formed using fewer, higher power transmit elements. REFERENCES. Kaiser, Julius A., Retrodirective Antenna System, ITC Conference Program, Las Vegas, NV, July, Kaiser, Julius A., Single Beam Synthesis from Thinned Arrays, Journal of the Acoustical Society of America. Vol. 76, No., August 984, pp U.S. Patent 5,9,84, Signal Processor for Elimination of Sidelobe Responses and Generation of Error Signals, assigned to FH&A.

7 8.40 GHz 6x6 Receive Array G=6 db x=sensor Elements t RF t) RF t) X X X X X RF + t) 50 MHz t) X TRANSMIT 5 G = 0 db XMT GHz from sensor elements 8.40 GHz SIGNAL PROCESSOR RF t) 50 MHZ 4 - t) XMT GHz 4.5 GHz SFs (H) FROM SIGNAL PROCESSING SUMMER SFs (V) FROM SIGNAL PROCESSING IF 4.5 GHz IF 4.5 GHz IF - 4 IF 4.5 GHz IF 4.5 GHz IF + PHASE COMBINERS IF MHz RECEIVE BEAM OUTPUT t) LO.40 GHz LO 5.55 GHz 8.40 GHz IF = 5.0 GHz IF =.8875 GHz Figure. Automatic Ground Station Antenna System

8 Rcv Array 6X6 els G = 6 db Rcv Array 6X6 els G = 6 db Rcv Array 6X6 els G = 6 db PLAN VIEW Rcv Array 6X6 els G = 6 db Transmit Array 960 els G = 0 db BEACON ANTENNA 50 deg ELEVATION VIEW Rcv Array 6X6 els G = 6 db 45 deg 45 deg Figure 4. Ground Station Antenna Arrays

9 I I sin ( I ) sin( ) Figure 5. Error Signal